Linearly moving operating devices have a wide field of use. The term linearly moving operating device shall be understood to include pressure fluid cylinders that operate with compressible media, such as compressed air. Linearly moving operating devices shall also be understood to include hydraulic cylinders and so-called ball screws. In the case of the first-mentioned operating devices, i.e. devices that work with compressible media, serious difficulties are experienced in braking and holding the piston-rod in desired positions. By braking is meant both progressive retardation of the piston and abrupt braking or holding the piston stationary. Examples of different solutions for braking the movement of pressure cylinders, particularly pneumatically operated cylinders, are found described in Swedish Patent Specifications 465 530, 465 888 and 465 899. These solutions include the use of a bar or rail along which a slide guided by the rail and connected to the piston of the cylinder can be locked. The solutions proposed, however, are relatively complicated and therewith expensive to implement, and the locking force generated by such devices is much too low to ensure safety in vertical applications.
The present invention, as defined in the characterizing clauses of respective claims, provides brake means for, e.g., compressed air cylinders and corresponding linearly moving operating devices that is of simple construction and highly reliable in operation by virtue of the very significant locking force generated by said brake means.